It is well-known to control light, e.g. ambient light, with the purpose of reflecting properties of an audio signal, e.g. the properties of music with the goal of creating an audio-visual perception of matching light and music. This is done for example at musical concerts, in restaurants, bars and discotheques.
At concerts, complex light sequences are normally carefully planned to perfectly match the musical content and thus manual skills and planning are required to obtain such result. On the contrary, light shows at discotheques or bars are often automatically controlled by detected signal parameters of the music signal. Such light control may be performed by detecting an overall level of the audio signal and adjust intensity of light accordingly, thus creating the overall experience of light flashing along with the beat of the music. Another example is to detect a level of the audio signal in three frequency bands: bass, midrange, and treble, each having assigned a light color whose intensity is controlled by the respective detected levels.
The described automatic light control methods are simple to implement, e.g. in analog electronics, and it is possible to control light on-line in response to an audio signal without an operator available. However, such low-level methods do not provide a universal agreement between musical content and light, especially not for a large variety of audio signals, e.g. classical music versus dance music or speech.